The accurate separation of tumour tissue from non-tumour tissue is a prerequisite for laboratory molecular analysis of many types of tumour tissues.
In standard laboratory practice, tumour tissue for analysis is obtained by cutting a thin tissue section from a formalin fixed, paraffin embedded (FFPE) tissue block known to contain tumour and non-tumour tissue, and preparing the tissue section on a glass histology slide. The tissue section will usually be cut with a thickness of approximately 5 μm or any other appropriate thickness to allow the outline of tissue structures to be made out by viewing the slide under a standard laboratory microscope.
In order to determine a boundary of a tumour region of a tissue section, it has been proposed to prepare a histology slide with the tissue section, comprising staining the tissue section with a laboratory dye and covering with a glass cover slip according to standard laboratory practice, for viewing and analysis by a trained pathologist. A method of marking tumour regions of the tissue section comprises the pathologist viewing the slide using a standard laboratory microscope and, based on subjective assessment, for example based on memory or on visual comparison with a look-up chart, identifying regions of the tissue section appearing to correspond to model tumour structures, and indicating boundaries of the regions via a manual annotation with a marker pen on the glass coverslip. Following annotation, a sequential tissue section, preferably having a thickness in the range indicated above, is cut from the tissue block and prepared on a second histology slide. Using the annotated slide as a template, tissue is manually scraped, using a scalpel, from a region of the sequential tissue section contained within an area corresponding to an annotated region.
The above process is manual in nature and relies upon subjective input from the pathologist to annotate the tumour area. Internal validation studies have indicated a high degree of both intra and inter-pathologist variation in this manual annotation process.